<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>

<body>
  <script>
    var str = '<div>{{name}}今年{{ age }}岁了</div>'
    var pattern = /{{\s*([a-zA-Z]+)\s*}}/

    var patternResult = null
    while (patternResult = pattern.exec(str)) {
      str = str.replace(patternResult[0], patternResult[1])
    }
    console.log(str)
  </script>
</body>

</html>